What is the best way to convert and update document fields in MongoDB to GeoJSON format using Java?

Question

What is the best way to convert and update document fields in MongoDB to GeoJSON format using Java?

I have a collection in mongodb that stores information about airports and I need to perform some Geospatial Queries.

One example document from this collection looks like this:

    {
            "_id" : ObjectId("528e8134556062edda12ffe6"),
            "id" : 6523,
            "ident" : "00A",
            "type" : "heliport",
            "name" : "Total Rf Heliport",
            "latitude_deg" : 40.07080078125,
            "longitude_deg" : -74.9336013793945,
            "elevation_ft" : 11,
            ...
    }

I want to transform all documents in the collection to have a structure like this:

    {
      "_id": ObjectId("528e8134556062edda12ffe6"),
      "id" : 6523,
      "ident" : "00A",
      "type" : "heliport",
      "name" : "Total Rf Heliport",
      "longitude_deg" : 17.27,
      "latitude_deg" : 52.22,
      "loc" : {
        "type" : "Point",
        "coordinates" : [
          17.27,
          52.22
        ]
      },
      ...
    }

The provided javascript code should achieve this transformation:

    var cursor = db.airports.find()

    cursor.forEach(function(input) {
      x = input.latitude_deg;
      y = input.longitude_deg;
      id = input._id;
      db.airports.update({"_id":id},{$set:{"loc":{"type":"Point","coordinates":[y,x]}}});
    });

However, I am struggling to create a Java program that accomplishes the same task. If anyone can provide guidance on how to solve this problem, it would be greatly appreciated.

Thank you in advance for your help and apologies for any language barriers!

java javascript mongodb geospatial

Answer 1

Answer №1

To demonstrate this process, I have developed a sample application using the MongoDB Inc. driver (legacy) as well as the Asynchronous Java Driver.

In the case of the asynchronous driver, I showcase two different approaches: synchronous and asynchronous. The primary distinction between the two is that in the synchronous/legacy scenario, you must wait for each update to finish. On the other hand, with the asynchronous model, you can proceed with other tasks while document fetching and updates occur in the background.

HTH, Rob.

P.S. Full disclosure: I am involved with the Asynchronous Java Driver.

package geojson.sof20181050;

import java.io.IOException;
import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.concurrent.Phaser;
import java.util.concurrent.atomic.AtomicLong;

...

...

Answer 2

To demonstrate this process, I have developed a sample application using the MongoDB Inc. driver (legacy) as well as the Asynchronous Java Driver.

In the case of the asynchronous driver, I showcase two different approaches: synchronous and asynchronous. The primary distinction between the two is that in the synchronous/legacy scenario, you must wait for each update to finish. On the other hand, with the asynchronous model, you can proceed with other tasks while document fetching and updates occur in the background.

HTH, Rob.

P.S. Full disclosure: I am involved with the Asynchronous Java Driver.

package geojson.sof20181050;

import java.io.IOException;
import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.concurrent.Phaser;
import java.util.concurrent.atomic.AtomicLong;

...

...

Answer 3

Answer №2

Thank you for your response. I made a few changes to the legacy driver method, but encountered this error:


import java.io.IOException;
import java.util.ArrayList;
import com.mongodb.BasicDBObject;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.DBObject;
import com.mongodb.MongoClient;
import com.mongodb.WriteConcern;

public class Geo {

    public static void main(final String[] args) throws InterruptedException,
            IOException {

        MongoClient mongoClient = new MongoClient("127.0.0.1", 27017);

        DB db = mongoClient.getDB("test");

        DBCollection coll = db.getCollection("airports2");


        try {
            int count = 0;
            for (final DBObject doc : coll.find()) {
                final Object id = doc.get("_id");
                final Number lat = Double.parseDouble(doc.get("latitude_deg").toString());
                final Number lon = Double.parseDouble(doc.get("longitude_deg").toString());

                final BasicDBObject query = new BasicDBObject();
                query.append("_id", id);

                final ArrayList coordinates = new ArrayList();
                coordinates.add(lon.doubleValue());
                coordinates.add(lat.doubleValue());
                final BasicDBObject geojson = new BasicDBObject("type", "Point");
                geojson.append("coordinates", coordinates);
                final BasicDBObject set = new BasicDBObject("loc", geojson);
                final BasicDBObject update = new BasicDBObject("$set", set);

                coll.update(query, update, false, false, WriteConcern.ACKNOWLEDGED);

                count += 1;
            }
            System.out.printf("Updated %d documents via the legacy driver.%n",
                    count);
        }
        finally {
            // Always close the client.
            mongoClient.close();
        }
    }

}

Although it works, the number of updated documents is different from db.airports.count(), which concerns me.

I am using the "airports" collection from this source.

Answer 4

Thank you for your response. I made a few changes to the legacy driver method, but encountered this error:


import java.io.IOException;
import java.util.ArrayList;
import com.mongodb.BasicDBObject;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.DBObject;
import com.mongodb.MongoClient;
import com.mongodb.WriteConcern;

public class Geo {

    public static void main(final String[] args) throws InterruptedException,
            IOException {

        MongoClient mongoClient = new MongoClient("127.0.0.1", 27017);

        DB db = mongoClient.getDB("test");

        DBCollection coll = db.getCollection("airports2");


        try {
            int count = 0;
            for (final DBObject doc : coll.find()) {
                final Object id = doc.get("_id");
                final Number lat = Double.parseDouble(doc.get("latitude_deg").toString());
                final Number lon = Double.parseDouble(doc.get("longitude_deg").toString());

                final BasicDBObject query = new BasicDBObject();
                query.append("_id", id);

                final ArrayList coordinates = new ArrayList();
                coordinates.add(lon.doubleValue());
                coordinates.add(lat.doubleValue());
                final BasicDBObject geojson = new BasicDBObject("type", "Point");
                geojson.append("coordinates", coordinates);
                final BasicDBObject set = new BasicDBObject("loc", geojson);
                final BasicDBObject update = new BasicDBObject("$set", set);

                coll.update(query, update, false, false, WriteConcern.ACKNOWLEDGED);

                count += 1;
            }
            System.out.printf("Updated %d documents via the legacy driver.%n",
                    count);
        }
        finally {
            // Always close the client.
            mongoClient.close();
        }
    }

}

Although it works, the number of updated documents is different from db.airports.count(), which concerns me.

I am using the "airports" collection from this source.

What is the best way to convert and update document fields in MongoDB to GeoJSON format using Java?

Answer №1

Answer №2

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